Balancing charge between battery pack system modules in a battery

ABSTRACT

A system for balancing a plurality of battery pack system modules connected in series comprising: a plurality of battery pack system modules, wherein a high charge module of the plurality of battery pack system modules has a charge greater than a that of other modules. At least one zener diode connected in series with a current limiting resistor is connected in parallel to the plurality of battery pack system modules. A power source is in communication with a disconnect circuit of at least one of the battery pack system modules. The disconnect circuit is actuated when the battery pack system module reaches a predetermined state of charge. The zener diode enables current from the power source to bypass charged battery pack system modules to charge other battery pack system modules.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser.No. 12/417,435 to David Allen White et al., filed on Apr. 2, 2009, andentitled “System for Balancing a Plurality of battery Pack SystemModules Connected in Series.” This application claims priority to U.S.Provisional Application No. 61/054,882 to David Allen White et al.,filed on May 21, 2008, and entitled “System for Balancing Battery PackSystem Modules.”

TECHNICAL FIELD

The present disclosure generally relates to a system for balancing aplurality of battery pack system modules.

BACKGROUND

A need exists for a system for balancing battery pack system modulesthat balances states of charge of the battery pack system modulesautomatically, without requiring manual balancing during maintenanceoperations.

A further need exists for a system for balancing battery pack systemmodules in which each battery pack system module is independentlyself-balancing, without requiring communication with a master controlleror other battery pack system modules, obviating the need for a costlycentralized master controller, and the need for complex interconnectionbetween battery pack system modules.

A need also exists for a system for balancing battery pack systemmodules that enables individual battery pack system modules and groupsof battery pack system modules to be selectively removable andreplaceable, without interrupting charging of other battery pack systemmodules.

The present embodiments meet these needs.

SUMMARY

According to one embodiment, an apparatus includes a first battery packsystem module having a first terminal. The first battery pack systemmodule also includes a second terminal. The first battery pack systemmodule further includes a first battery cell in communication with thefirst terminal and the second terminal. The first battery pack systemmodule also includes a first charge switch in communication with thefirst terminal and the first battery cell, in which the first chargeswitch, when activated, disconnects the battery cell from the firstterminal to prevent charging of the battery cell. The first battery packsystem module further includes a first zener diode in communication withthe first terminal and the second terminal.

According to another embodiment, a method includes detecting that afirst battery pack system module has reached a first state of charge.The method also includes activating a first charge switch in the firstbattery pack system module to prevent further charging of the firstbattery pack system module after detecting the first state of charge.The method further includes passing current through a first zener diodein the first battery pack system module to a second battery pack systemmodule. The method also includes charging the second battery pack systemmodule.

According to yet another embodiment, a computer program product includesa computer-readable medium having code to detect that a first batterypack system module is at a first state of charge and a second batterypack system module is at a second state of charge lower than the firststate of charge during any mode of operation of the first and secondbattery pack system modules. The medium also includes code to activateat least one shunting resistor in communication with at least onebattery cell in the first battery pack system module during any mode ofoperation. The medium further includes code to deactivate the at leastone shunting resistor in communication with the at least one batterycell when the state of charge of the first battery pack system modulebecomes approximately equal with the state of charge of the secondbattery pack system module.

According to a further embodiment, a system for balancing a plurality ofbattery pack system modules connected in series includes a plurality ofbattery pack system modules connected in series, wherein a high chargemodule of the plurality of battery pack system modules has a chargegreater than a charge for other modules of the plurality of battery packsystem modules connected in series. The system also includes at leastone zener diode connected in series with a current limiting resistor,wherein the at least one zener diode is disposed between the high chargemodule and an adjacent module of the plurality of battery pack systemmodules, and wherein the at least one zener diode is in communicationwith a disconnect circuit of at least one of the plurality of batterypack system modules. The system further includes a power source incommunication with the disconnect circuit, wherein the disconnectcircuit is actuated when the at least one of the plurality of batterypack system modules reaches a predetermined state of charge, and whereinthe disconnect circuit stops current from the power source to theplurality of battery pack system modules. The current from the powersource is limited by the current limiting resistor. The at least onezener diode enables current from the power source to bypass at least oneof the plurality of battery pack system modules at the predeterminedstate of charge to charge at least one other battery pack system module.

According to another embodiment, a system for balancing a plurality ofbattery pack system modules connected in series includes a plurality ofbattery pack system modules connected in series, wherein a high chargemodule of the plurality of battery pack system modules has a chargegreater than a charge for other modules of the plurality of battery packsystem modules connected in series. Each battery pack system module ofthe plurality of battery pack system modules includes at least onebalancing circuit comprising a shunt resistor and a bypass switch,wherein the at least one balancing circuit is in communication with aplurality of cells connected in series. Each battery pack system modulealso includes at least one disconnect circuit comprising a chargeswitch, wherein the at least one disconnect circuit is in communicationwith the plurality of cells. Each battery pack system module furtherincludes a controller assembly in communication with the plurality ofcells connected in series. The controller assembly includes a digitalcontroller comprising a processor. The controller assembly also includesmeans for monitoring and measuring parameters for the plurality of cellsto determine a state of charge for each cell of the plurality of cells.The controller assembly further includes computer instructions forinstructing the processor to actuate and de-actuate the at least onebalancing circuit, the at least one disconnect circuit, or combinationsthereof, responsive to the parameters for the plurality of cells. Thecontroller assembly also includes computer instructions for instructingthe processor to actuate and de-actuate the charge switch of the atleast one disconnect circuit when one of the plurality of battery packsystem modules reaches a predetermined state of charge. The controllerassembly further includes computer instructions for instructing theprocessor to actuate and de-actuate the bypass switch of each at leastone balancing circuit to at least partially discharge at least one ofthe plurality of battery pack system modules when the at least one ofthe plurality of battery pack system modules reaches the predeterminedstate of charge. The controller assembly also includes a power source incommunication with the at least one disconnect circuit, wherein the atleast one disconnect circuit and the at least one balancing circuit areactuated when at least one of the plurality of battery pack systemmodules reaches the predetermined state of charge enabling at leastpartial discharge of the at least one of the plurality of battery packsystem modules and enabling charging of at least one other of theplurality of battery pack system modules, and wherein the at least onedisconnect circuit stops current from the power source to the pluralityof battery pack system modules.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims. The novel features which are believed to be characteristic ofthe invention, both as to its organization and method of operation,together with further objects and advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referenceis now made to the following descriptions taken in conjunction with theaccompanying drawings.

FIG. 1 depicts a diagram of an embodiment of a battery pack systemmodule useable with the present system.

FIG. 2 depicts a diagram of an embodiment of the present systemcontaining battery pack system modules connected in series, each havinga zener diode.

FIG. 3 depicts a diagram of an embodiment of the present systemcontaining groups of battery pack system modules connected in parallel,that are connected to other groups of battery pack system modules inseries.

FIG. 4 depicts a diagram of an embodiment of the present systemcontaining groups of battery pack system modules connected in series,that are connected to other groups of battery pack system modules inparallel.

FIG. 5 depicts a diagram of an embodiment of a method useable with anembodiment of the present system.

FIG. 6 depicts a diagram of an embodiment of a method useable with analternate embodiment of the present system.

DETAILED DESCRIPTION

Before explaining the present system in detail, it is to be understoodthat the system is not limited to the particular embodiments and that itcan be practiced or carried out in various ways.

The present embodiments relate to a system for balancing a plurality ofbattery pack system modules, which can be connected in series. Thepresent system can also be useable to balance multiple groups of batterypack system modules connected in parallel. Each group of parallelbattery pack system modules can be connected to other groups of batterypack system modules in series.

In conventional systems, when a single battery pack system module withina system of battery pack system modules connected in series reaches apredetermined state of charge, a disconnect circuit within the batterypack system module is actuated, preventing current from charging anyother battery pack system modules within the battery pack system.

This inability to charge other battery pack system modules can result inunbalanced battery pack systems, which can cause damage to the batterypack system modules and other equipment connected to the battery packsystem. Additionally, the existence of overcharged and unbalancedbattery pack system modules can present a safety hazard to personnelthat operate on the battery pack system modules and any attachedequipment.

Conventional battery pack system modules connected in series musttherefore be balanced manually, by interrupting operation of equipmentpowered by the battery pack system, fully discharging each battery packsystem module within the battery pack system, then simultaneouslycharging each battery pack system module. Manual balancing operationsare tedious, time consuming, and costly, and are therefore typicallyundertaken no more often than once every six months.

These special maintenance operations are often not performed due toinattention to detail or a lack of time, manpower, or other resourcesnecessary to perform the manual balancing operations. Failure to performthese balancing operations can allow individual battery pack systemmodules within a group of modules connected in series to attainunbalanced states of charge, potentially damaging one or more parts ofthe modules and any connected equipment, and creating a safety hazard tooperators of the battery pack system modules and connected equipment.

The present system advantageously enables a plurality of battery packsystem modules, which can be connected in series to independently andautomatically attain a balanced state of charge during a normal chargephase, without requiring separate special maintenance operations.Through use of the present system, the costly and time consuming needsfor manual balancing of the battery pack system modules is removedentirely.

The present system can use zener diodes connected in series with currentlimiting resistors to enable current from a power source toautomatically bypass battery pack system modules that have attained apredetermined state of charge. By enabling the bypass of charged batterypack system modules, the zener diodes enable the charging of otherbattery pack system modules connected in series within a system thathave not yet attained the predetermined state of charge. The presentsystem thereby automatically creates a balanced state of charge withinthe battery pack system once each battery pack system module hasattained the predetermined state of charge.

Additionally or alternatively, the present system can utilize computerinstructions for measuring the state of charge of a battery pack systemmodule, disconnecting a charge switch, and actuating shunt resistorswithin balancing circuits to partially discharge battery pack systemmodules that have attained a predetermined high state of charge. Theshunting of the battery pack system modules can be performed until themodules reach a hysteresis state of charge, at which time the chargeswitch can be reconnected, and charging of the battery pack system canresume.

By automatically partially discharging battery pack system modules thathave reached the predetermined high state of charge, the simultaneouscharging of each module within a battery pack system can be continuedwithout exceeding the predetermined high state of charge in any batterypack system module.

This embodiment of the present system produces an oscillating state ofcharge within the battery pack system modules, whereby once a batterypack system module has attained a predetermined high state of charge,the battery pack system module is partially discharged, then chargedsimultaneously with other battery pack system modules connected inseries. Once all battery pack system modules within a battery packsystem are charged to the predetermined high state of charge, creating abalanced system, it can be contemplated that all of the battery packsystem modules exhibit an oscillating state of charge simultaneously,through partial discharge using the balancing circuits, thensimultaneous charging from a power source.

It is contemplated that in an embodiment, the use of computerinstructions to automatically cause the partial discharge of batterypack system modules that have reached a predetermined high state ofcharge can be coupled with use of zener diodes connected to currentlimiting resistors. Using this embodiment, during discharge of a chargedbattery pack system module, current can continue to charge other batterypack system modules connected in series by bypassing the dischargingmodule through use of a zener diode, providing enhanced efficiency overthe use of zener diodes or partial discharge alone.

The present system can provide the advantage of enabling constant andcontinuous balancing of a plurality of battery pack system modulesconnected in series, automatically, each time a battery pack system ischarged. Typical balancing operations are only performed once every sixmonths, or even less frequently, generating a greater risk that abattery pack system will become unbalanced as time passes.

By enabling automatic balancing of a plurality of battery pack systemmodules connected in series, use of a battery pack system modulebalancing resistor, typically required for conventional balancingoperations, is not necessary. Attachment of a balancing resistor can bedisruptive to normal operation of a battery pack system.

Conventional systems require that each battery pack system module withina system communicates with one another through complex interconnections,or through a costly centralized master controller. The present systemcan enable each battery pack system module to independently attain abalanced state of charge with other battery pack system modulesconnected in series, without requiring centralized monitoring orcontrol, and without requiring any of the battery pack system modules tocommunicate with any other module.

The present system thereby provides the benefit of increased batterypack system design flexibility, while retaining battery pack systemmodule balance. Because each battery pack system module can beindependent of one another, battery pack system modules within a batterypack system can be removed and reconfigured in a modular fashion,allowing nearly unlimited flexibility in battery pack system designconfigurations.

The present system further provides the advantage of enabling batterypack system modules to be charged to a predetermined state of charge,such as about 80 percent of the maximum capacity for each battery packsystem module. By permitting balancing of battery pack system modules atselected predetermined states of charge, the lifespan of cells withineach battery pack system module can be prolonged significantly. Typicalrechargeable cells can be fully charged to their maximum capacity, thenfully discharged, approximately 1,000 times. By charging and balancingat a predetermined state of charge, using the present system, each cellcan be contemplated to have a life expectancy ranging from about 2,000charging cycles to about 10,000 charging cycles, or more.

Additionally, maintaining a battery pack system module's cells at apredetermined level of charge, such as about 80 percent of maximumcapacity, can increase useable life for a battery pack system moduleused in a mode where there are infrequent charge/discharge cycles, suchas a back-up mode, from a typical useable life of about 1 year to about2 years to a greater useable life of about 5 years to about 10 years.

Referring now to FIG. 1, a diagram of an embodiment of a battery packsystem module useable with the present system is depicted.

The battery pack system module is depicted having a battery pack controlmodule (6), which is useable to internally monitor and balance states ofcharge of a plurality of individual cells connected in series within thebattery pack system module. The battery pack control module (6) is alsouseable to monitor and balance groups of cells connected in parallel,the groups of cells connected to other groups of cells in series.

The battery pack control module (6) includes a controller assembly (8)for measuring parameters and controlling a disconnect circuit (12) andbalancing circuits (25 a, 25 b) responsive to parameters measured by thecontroller assembly (8) and a pack sensing circuit (21).

A voltage regulator (42), such as a DC programmable voltage regulatormade by Linear Technology, Inc. of Malpitas, Calif., can be used topower the controller assembly (8).

The battery pack control module (6) is shown having a protective diode(28), which can be a reverse voltage protection diode or a bypass diode,useable to protect cells within the depicted battery pack system modulefrom excessive voltage. Bypass diodes such as those manufactured by ONSemiconductor of Phoenix Ariz. or Vishay of Malvern, Pa. can becontemplated for use herein. The protective diode (28) can be connectedto the disconnect circuit (12), and to a first group of cells (20).

For example, the protective diode (28) can prevent damage to thedisconnect circuit (12) by shunting damaging negative voltage transientsaround the disconnect circuit (12).

The disconnect circuit (12) is depicted having a charge switch (13) anda discharge switch (14), which can be transistor switches, such as aVishay P-FET switch, made by Vishay of Malvern, Pa., or similar types ofswitches. The disconnect circuit (12) can be in communication with asecond group of cells (19).

The first group of cells (20) is shown having a first lithium ion cell(17) and a second lithium ion cell (18), which can be connected inparallel. The first group of cells (20) can be connected in series tothe second group of cells (19). The second group of cells (19) is shownhaving a third lithium ion cell (15) and a fourth lithium ion cell (16),which can be connected in parallel.

While each group of cells (19, 20) is shown including two individualcells connected in parallel, it is contemplated that a group of cellscan have any number of cells, such as from about one cell to about fourcells, or more.

FIG. 1 depicts each of the cells (15,16,17,18) as lithium ion cells,such as lithium ion cells having a nominal voltage of about 3.7 voltsmade by Tianjin Lishen Battery Joint-Stock Co. Ltd., of Tianjin Huayuan,China. It can be contemplated that the present system can be useablewith any type of rechargeable cell, including nickel cadmium cells,nickel metal hydride cells, lead acid cells, and other similarrechargeable cells.

In an embodiment, one or more battery pack system modules can includeone or more capacitors, one or more supercapacitors, one or moreelectrochemical cells, such as fuel cells, or combinations thereof, inaddition to the plurality of cells (15, 16, 17, 18). The one or morecapacitors, one or more supercapacitors, one or more electrochemicalcells, or combinations thereof can also be included in place of theplurality of cells (15, 16, 17, 18).

A zener diode (49), such as a high power zener diode manufactured by ONSemiconductor of Phoenix, Ariz., can be connected in series with acurrent limiting resistor (51), such as a current limiting resistorhaving a power capability of five watts or more, manufactured by Vishayof Malvern, Pa. The zener diode (49) and current limiting resistor (51)can be connected in parallel to the protective diode (28) and can be incommunication with the disconnect circuit (12).

It is contemplated that the zener diode (49) and current limitingresistor (51) can be disposed between adjacent battery pack systemmodules within a group of battery pack system modules connected inseries. The zener diodes can be contemplated to permit the flow ofcurrent from a power source, shown in FIG. 1 as a charger (48) through abattery pack system module that has reached a predetermined state ofcharge without charging the battery pack system module, thereby allowingthe charging of other battery pack system modules connected in series.

The zener diode (49)_can permit the flow of current that would otherwisebe stopped by actuation of the disconnect circuit (12), enablingcharging of other battery pack system modules connected in series withthe depicted battery pack system module. For example, when thedisconnect circuit (12) is actuated, a current of 250 ma can bepermitted to flow through the current limiting resistor (51) and thezener diode (49) to charge one or more adjacent battery pack systemmodules.

The controller assembly (8) is shown having an analog controller (9),such as Part Number BQ29312A, available from Texas Instruments ofDallas, Tex., and a digital controller (10). The digital controller (10)can include analog and digital input/output ports, a processor, whichcan be a microprocessor, memory, which can include flash memory andprocessing logic located in the memory, and computer instructions forexecuting balancing, measuring, charging, and discharge functions.

The analog controller (9) is shown having a measuring device (24), whichcan be contemplated to measure the voltage of individual cells or groupsof cells within the battery pack system module, or the voltage of theentire battery pack system module.

The controller assembly (8) can be in communication with the packsensing circuit (21), which is shown having a current measuring device(23) and a temperature measuring device (22). The voltage, current, andtemperature measurements obtained using the measuring devices (22, 23)can be used by the digital controller (10) to obtain the state of chargeof the battery pack system module. The state of charge can be related tovoltage, current, and/or temperature as relative capacity through datatables within configuration memory (46).

It is contemplated that the pack sensing circuit (21) can measuretemperatures ranging from about −50 degrees Centigrade to about 85degrees Centigrade or more, current ranging from about 0 ma to about16,000 ma or more, and voltage ranging from about 0 V to 18 about V ormore.

The state of charge indicates the percent charge of the battery packsystem module relative to the nominal maximum charge of the battery packsystem module. The state of charge can also be measured as absolutecapacity by additionally measuring the time average current into and outof the entire battery pack system module to obtain the number ofamperage hours remaining in the battery pack system module.

In an embodiment, the measured state of charge of the battery packsystem module can be an absolute state of charge determined by countingcoulombs, such as an absolute capacity of 24 ampere hours based on theflow of coulombs from a power source.

The state of charge and status of the battery pack system module can beacquired and externally displayed using an initializer or display device(50), such as a monitor made by Hewlett Packard of Palo Alto, Calif.,which can be in communication with the controller assembly (8).

The state of charge and status of the battery pack system module can beexternally displayed using an external display device (5). The externaldisplay device (5) can include one or more light emitting diodes, suchas 4 mm oval red LEDs made by Ledman Optoelectronic Co., Ltd., ofChina., a liquid crystal display, such as one made by Sony Electronics,Inc., a plasma display, such as one made by Ningbo Boigle DigitalTechnology Co., Ltd., of China, or combinations thereof. Use of a liquidcrystal display can be contemplated to be advantageous for applicationswhen lower power consumption is required, such as military applications.

An internal display (11), a liquid crystal display, a plasma display, orcombinations thereof can be in communication with the controllerassembly (8). The internal display (11) and the external display (5) canbe useable separately or together to visibly display status and capacityparameters of the battery pack system module for use by operators andother users.

A first balancing circuit (25 a) is shown having a first shunt resistor(26 a) and a first by-pass switch (27 a) can be in communication withthe controller assembly (8) and the first group of cells (20). A secondbalancing circuit (25 b) is shown having a second shunt resistor (26 b)and a second by-pass switch (27 b) can be in communication with thecontroller assembly (8) and the second group of cells (19).

The by-pass switches (27 a, 27 b) can include semiconductor switches,variable resistors, mini-micro switches, or combinations thereof.

The balancing circuits (25 a, 25 b) can be contemplated to be useable tobalance the states of charge of the groups of cells (19, 20). Thebalancing circuits (25 a, 25 b) can also be contemplated to be useableto at least partially discharge the depicted battery pack system moduleto facilitate balancing of a plurality of battery pack system 10 modulesconnected in series.

FIG. 1 depicts a power source (48), which is shown as a charger,connected to the first group of cells (20) and to the disconnect circuit(12). The power source (48) can include any type of current limited andvoltage limited power source, including one or more solar panels, fuelcells, or any other current limited power supply with voltage foldback,such as a Lambda GENH 40-19 or the equivalent.

The controller assembly (8) can include computer instructions (44),which can be stored in flash memory or using other means, forinstructing the processor of the digital controller (10) to actuate andde-actuate the disconnect circuit (12) in response to voltage, current,and temperature measurements obtained from the measuring devices (22,23, 24).

The computer instructions (44) can also instruct the processor of thedigital controller (10) to actuate and de-actuate the balancing circuits(25 a, 25 b) and the disconnect circuit (12) to balance states of chargeof the groups of cells (19, 20), allowing the safe charge and internalbalancing of the cells within the depicted battery pack system module.

The controller assembly (8) can further includes configuration memory(46), such as flash memory, that can be loaded by the initializer ordisplay device (50), that can contain battery pack system module designparameters, such as cell chemistry parameters, application parameters,charge parameters, discharge parameters, and other similar parameters.The provision of the configuration memory (46) can enable the designingof battery pack system modules with unique specifications andcharacteristics.

The controller assembly (8) can further include computer instructions(45), which can be stored in flash memory, or using other means, whichcan be used to balance the state of charge of the depicted battery packsystem module with that of other battery pack system modules connectedto the depicted battery pack system module in series.

The computer instructions (45) can be contemplated to instruct theprocessor of the digital controller (10) to measure the state of chargeof the battery pack system module using one or more of the measuringdevices (22, 23, 24) and display the state of charge on the initializeror display device (50).

The computer instructions (45) can also instruct the processor of thedigital controller (10) to actuate and de-actuate the charge switch (13)of the disconnect circuit (12) when the battery pack system modulereaches a predetermined state of charge. For example the charge switch(13) can be actuated when a solar cell battery reaches a predeterminedstate of charge of about 80 percent to about 85 percent relativecapacity, the predetermined charge selected to prolong the life of thebattery.

The computer instructions (45) can further instruct the processor of thedigital controller (10) to actuate and de-actuate the by-pass switches(27 a, 27 b) of each of the balancing circuits (25 a, 25 b) when thebattery pack system module reaches the predetermined state of charge,thereby at least partially discharging the battery pack system moduleusing the shunt resistors (26 a, 26 b)

The present system thereby can utilize the shunt resistors (26 a, 26 b)for the dual purposes of balancing the state of charge of individualcells within the battery pack system module, and for at least partiallydischarging all cells of the battery pack system module to balance thestate of charge of the battery pack system module with that of otherbattery pack system modules connected in series.

The computer instructions (45) can be contemplated to actuate the shuntresistors (26 a, 26 b) of each balancing circuit (25 a, 25 b) when thebattery pack system module is charged to a predetermined high state ofcharge, causing discharge of the battery pack system module, and tode-actuate the shunt resistors (26 a, 26 b) to cease the discharge ofthe battery pack system module when the battery pack system module hasbeen discharged to a predetermined hysteresis charge.

For example, when a battery pack system module reaches a predeterminedhigh state of charge of about 85 percent relative capacity, eachbalancing circuit within the battery pack system module can be actuatedto discharge the battery pack system module to a hysteresis charge ofabout 83 percent relative capacity, at which time the balancing circuitscan be de-actuated to cease discharge of the battery pack system module.

Referring now to FIG. 2, a diagram depicting an embodiment of thepresent system is shown.

FIG. 2 depicts a battery pack system (40), which can include a pluralityof battery pack system modules. FIG. 2 shows a first battery pack systemmodule (202 a) connected in series with a second battery pack systemmodule (202 b), and a third battery pack system module (202 c).

While FIG. 2 depicts the battery pack system (40) is shown having threebattery pack system modules, it can be contemplated that a battery packsystem can include any number of battery pack system modules, such asfrom about 1 battery pack system module to about 15 battery pack systemmodules, or more, depending on the voltage requirements of the system.

For example, when a voltage of 200 volts is required in an automobile, asufficient number of battery pack system modules connected in series, orgroups of battery pack system modules connected in parallel that areconnected to other groups in series can be provided, that provide atotal nominal voltage of at least 200 volts.

Each battery pack system module (202 a, 202 b, 202 c) can include anynumber of individual cells. In an embodiment, from about one cell toabout four cells connected in series can be contained in each batterypack system module, such that each battery pack system module provides anominal voltage ranging from about 3.7 volts to about 14.8 volts. Whenfully charged, each battery pack system module can provide from about4.2 volts to about 16.8 volts, and when empty, from about 3 volts toabout 12 volts.

It can be contemplated that one battery pack system module of theplurality of battery pack system modules can be a high charge module,having reached a predetermined level of charge greater than that ofother battery pack system modules, such as by about 1 percent to about50 percent or more when a system is extremely unbalanced, by about 1percent to about 20 percent when a system is significantly unbalanced,or about 1 percent to about 5 percent when a system is moderatelyunbalanced. The predetermined level of charge can be the maximum levelof charge for the battery pack system module, or another level specifiedby a user and/or manufacturer, such as about 80 percent relativecapacity for the battery pack system module.

For example, a high charge battery pack system module (202 a) can becharged to a predetermined high state of charge of about 90 percentrelative capacity, while an adjacent battery pack system module (202 b)can have a charge of about 89 percent 20 relative capacity, and the nextadjacent battery pack system module (202 c) can have a charge of about60 percent relative capacity.

In this situation, current from a charger (48) conducted to the highcharge battery pack system module (202 a) can bypass the high chargebattery pack system module (202 a) via a zener diode contained withinthe high charge battery pack system module (202 a) to charge theadjacent battery pack system modules (202 b, 202 c). When the secondbattery pack system module (202 b) has reached the predetermined levelof about 90 percent relative capacity, current from the charger (48) canbypass the second battery pack system module (202 b) via a zener diodecontained within the second battery pack system module (202 b) to chargethe third battery pack system module (202 c).

Referring now to FIG. 3, a diagram depicting an alternate embodiment ofthe present system is shown.

FIG. 3 depicts a first group of battery pack system modules (40 a),which can include a first battery pack system module (202 a) and asecond battery pack system module (202 b) connected in parallel.

FIG. 3 also depicts a second group of battery pack system modules (40b), which can include a third battery pack system module (202 c) and afourth battery pack system module (202 d) connected in parallel.

The first group of battery pack system modules (40 a) can be connectedin series with the second group of battery pack system modules (40 b).

While FIG. 3 depicts two groups of battery pack system modules connectedin series, each group containing two battery pack system modulesconnected in parallel, it can be contemplated that each group caninclude any number of battery pack system modules connected in series orin parallel, and that any number of groups of modules can be in turnconnected in series or in parallel.

FIG. 3 depicts a charger (48) for providing current to each of thebattery pack system modules (202 a, 202 b, 202 c, 202 d). In theembodiment, it is contemplated that each battery pack system module canlack a zener diode. It can be contemplated that each battery pack systemmodule can include balancing circuits having shunt resistors. Computerinstructions can be within each battery pack system module and can causethe shunt resistors to be actuated when the battery pack system modulereaches a predetermined level of charge, causing the battery pack systemmodule to be at least partially discharged.

After partial discharge of the battery pack system module, current fromthe charger (48) can again simultaneously charge each of the batterypack system modules (202 a, 202 b, 202 c, 202 d) until one or more ofthe battery pack system modules reaches the predetermined state ofcharge.

For example, if the first and second battery pack system modules (202 a,202 b) reach a predetermined state of charge of about 90 percentrelative capacity, prior to the third and fourth battery pack systemmodules (202 c, 202 d), which have reached about 82 percent relativecapacity, the first and second battery pack system modules (202 a, 202b) can be partially discharged by a predetermined amount, automatically,through use of computer instructions to actuate balancing circuits.

The first and second battery pack system modules (202 a, 202 b) can bedischarged to a hysteresis value of about 86 percent relative capacity.Then, charging of the entire battery pack system could be resumed, untilthe first and second battery pack system modules (202 a, 202 b) againreach about 90 percent relative capacity, while the third and fourthbattery pack system modules (202 c, 202 d) reach about 86 percentrelative capacity.

The first and second battery pack system modules (202 a, 202 b) canagain be discharged to about 86 percent relative capacity, and chargingof the entire battery pack system would continue until each battery packsystem module (202 a, 202 b, 202 c, 202 d) reaches the predeterminedstate of charge of about 90 percent relative capacity. All four batterypack system modules (202 a, 202 b, 202 c, 202 d) can then be balancedand would proceed to charge to the predetermined 90 percent capacity anddischarge to about 86 percent capacity together, until the charger (48)is disconnected.

Referring now to FIG. 4, a diagram depicting an alternate embodiment ofthe present system is shown.

FIG. 4 depicts a first group of battery pack system modules (40 a),which can include a first battery pack system module (202 a) and asecond battery pack system module (202 b) connected in series.

FIG. 4 also depicts a second group of battery pack system modules (40b), which can include a third battery pack system module (202 c) and afourth battery pack system module (202 d) connected in series.

The first group of battery pack system modules (40 a) can be connectedin parallel with the second group of battery pack system modules (40 b).

A charger (48) is shown for providing current to each group of batterypack system modules (40 a, 40 b) simultaneously.

It can be contemplated that the design flexibility provided by thepresent system enables any number of battery pack system modules to bestackable, and to be connected in any number of series and/or parallelconfigurations to provided a desired amount of voltage.

It can be contemplated that the design flexibility provided by thepresent system enables any number of battery pack system modules to bestackable, and to be connected in any number of series and/or parallelconfigurations to provided a desired amount of voltage.

Referring now to FIG. 5, a diagram showing an embodiment of a methoduseable with an embodiment of the present system is shown.

FIG. 5 depicts that current can be provided to a battery pack systemcontaining multiple battery pack system modules until a first batterypack system module reaches a predetermined state of charge (300).

Once the first battery pack system module reaches a predetermined stateof charge, a charge switch in the first battery pack system module canbe opened to prevent further charging of the first battery pack systemmodule and other series connected modules (302).

Current from the charger can be carried to other battery pack systemmodules in the battery pack system using a zener diode within the firstbattery pack system module (304), thereby enabling the remaining moduleswithin the battery pack system to continue charging when the firstbattery pack system module has been disconnected from the charger.

Charge switches in other battery pack system modules can be opened whenthe other battery pack system modules reach the predetermined state ofcharge (306).

Zener diodes within each charged battery pack system module can be usedto carry the current of the battery pack system modules that havereached the predetermined state of charge, so that the battery backsystem can continue to be charged until the entire system has reachedthe predetermined state of charge (308).

FIG. 6 depicts a diagram showing an embodiment of a method useable withan alternate embodiment of the present system.

FIG. 6 depicts that current can be provided to a battery pack systemcontaining multiple battery pack system modules until a first batterypack system module reaches a predetermined high state of charge (400).

Computer instructions can be within the first battery pack system moduleand can then be used to disconnect the charge switch in the firstbattery pack system module to prevent further charging of the firstbattery pack system module and other series connected modules, and toactuate shunt resistors within the first battery pack system module toat least partially discharge the first battery pack system module to apredetermined hysteresis state of charge (402). This action can preventbattery pack system module cells from over charging and provides forinitiation of charge/discharge cyclic oscillation.

Continued charging of the first battery pack system module is therebyable to be resumed, then stopped as the first battery pack system moduleis at least partially discharged in a cyclic charge/dischargeoscillating fashion, such that the first battery pack system moduleoscillates between the predetermined high state of charge and thehysteresis state of charge continuously, as long as a charge source isconnected.

Other battery pack system modules that have not obtained thepredetermined high state of charge can be charged but not dischargeduntil each reaches the predetermined high state of charge (404).

At that time, computer instructions can be used to actuate shuntresistors within each battery pack system module to at least partiallydischarge each battery pack system module that reaches the predeterminedhigh state of charge (406). The battery pack system can be balanced onceeach module has reached the predetermined high state of charge andbegins its charge/discharge oscillation.

Once all battery pack system modules within a battery pack system arecharged to the predetermined high state of charge, creating a balancedsystem, it can be contemplated that all of the battery pack systemmodules exhibit an oscillating state of charge simultaneously, throughpartial discharge to a hysteresis state of charge using the shuntresistors, then simultaneous charging until the predetermined high stateof charge can be again reached.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutions,and alterations can be made herein without departing from the spirit andscope of the disclosure as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods, and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thepresent disclosure, processes, machines, manufacture, compositions ofmatter, means, methods, or steps, presently existing or later to bedeveloped that perform substantially the same function or achievesubstantially the same result as the corresponding embodiments describedherein may be utilized according to the present disclosure. Accordingly,the appended claims are intended to include within their scope suchprocesses, machines, manufacture, compositions of matter, means,methods, or steps.

What is claimed is:
 1. A method, comprising: detecting that a firstbattery pack system module comprising a plurality of battery cells hasreached a first state of charge by the first battery pack system module;activating, by the first battery pack system module, a first chargeswitch in the first battery pack system module to physically disconnectand to prevent further charging of the first battery pack system moduleafter detecting the first state of charge; discharging the plurality ofbattery cells after activating the first charge switch to balance thefirst battery pack system module with a second battery pack systemmodule connected in series with the first battery pack system module;de-activating, by the first battery pack system module, the first chargeswitch after discharging the plurality of battery cells to a lower stateof charge; and charging the first battery pack system module andcharging the second battery pack system module after de-activating thefirst charge switch.
 2. The method of claim 1, further comprising:passing current through a first zener diode in the first battery packsystem module to a second battery pack system module connected in serieswith the first battery pack system module; and limiting current throughthe first zener diode to a level below a limit of the zener diode. 3.The method of claim 1, further comprising providing current to the firstbattery pack system module and the second battery pack system modulethrough a terminal of the first battery pack system module and aterminal of the second battery pack system module.
 4. The method ofclaim 1, in which the detecting step comprises detecting the firstbattery pack system module is at a first state of charge unbalanced witha second state of charge of the second battery pack system module duringany mode of operation of the first battery pack system module.
 5. Themethod of claim 1, further comprising: detecting, by the second batterypack system module, that the second battery pack system module hasreached a second state of charge; and activating, by the second batterypack system module, a second charge switch in the second battery packsystem module to prevent further charging of the second battery packsystem module after detecting the second state of charge.
 6. The methodof claim 1, further comprising balancing battery cells within the firstbattery pack system module.
 7. The method of claim 6, in which the stepof balancing the battery cells within the first battery pack systemmodule comprises activating a shunting resistor in communication with atleast one battery cell to discharge the at least one battery cell. 8.The method of claim 1, in which the step of activating the first chargeswitch comprises a controller of the first battery pack system moduleactivating a disconnect circuit of the first battery pack system module,and in which the step of detecting comprises the controller of the firstbattery pack system module communicating with a pack sensing circuit ofthe first battery pack system module.
 9. The method of claim 1, furthercomprising: detecting the first battery pack system module and thesecond battery pack system module are approximately balanced; andoscillating through a sequence defined by: charging the first batterypack system module and the second battery pack system module for a firstperiod of time; and discharging the first battery pack system module andthe second battery pack system module for a second period of time. 10.The method of claim 1, further comprising: balancing a first pluralityof cells in the first battery pack system module with a first controllerassembly of the first battery pack system module; and balancing a secondplurality of cells in the second battery pack system module with asecond controller assembly of the second battery pack system module. 11.The method of claim 1, in which the step of discharging the plurality ofbattery cells comprises activating a shunting resistor in communicationwith the plurality of battery cells to discharge each of the pluralityof battery cells.
 12. The method of claim 11, in which the step ofactivating a shunting resistor comprises activating a plurality ofshunting resistors in communication with the plurality of battery cellsto discharge each of the plurality of battery cells simultaneously. 13.The method of claim 1, in which the step of discharging the plurality ofbattery cells comprises discharging the plurality of battery cells to apredetermined state of charge.
 14. A computer program product,comprising: a computer-readable medium comprising: code to detect that afirst battery pack system module comprising a plurality of battery cellsis at a first state of charge and a second battery pack system module,connected in series with the first battery pack system module, is at asecond state of charge lower than the first state of charge; code toactivate, by the first battery pack system module, a first charge switchin the first battery pack system module to physically disconnect and toprevent further charging of the first battery pack system module afterdetecting that the first battery pack system module is at a first stateof charge higher than a second state of charge of the second batterypack system module; code to activate at least one shunting resistor incommunication with at least one battery cell in the first battery packsystem module to discharge the plurality of battery cells of the firstbattery pack system module; and code to deactivate the at least oneshunting resistor in communication with the at least one battery cellwhen the first state of charge of the first battery pack system modulebecomes approximately equal with the second state of charge of thesecond battery pack system module.
 15. The computer program product ofclaim 14, in which the medium further comprises code to balance batterycells within the first battery pack system module during any mode ofoperation of the first battery pack system module.
 16. The computerprogram product of claim 15, in which the medium further comprises codeto activate at least one shunting resistor in communication with atleast one battery cell to discharge the at least one battery cell duringany mode of operation of the first battery pack system module.